According to a UW-Madison study, meditation can reduce the incidence, duration and severity of colds and the flu by about 30 percent to 60 percent.
It seems strange that our society spends so much time and energy to prove what seems intuitively obvious. They could have spent that time meditating! I am grateful for this work nonetheless, as studies like these can be a point of entry for skeptics (Especially given that I am a recovering skeptic myself.) Click to read the details here.